Infusion device and driving mechanism for same

• US 20050245907A1
• Filed: 06/29/2005
• Published: 11/03/2005
• Est. Priority Date: 09/07/2001
• Status: Abandoned Application

• Current Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Inventors: Bosley, Robert W., Gray, John F.
• Application Number:
  US11/171,587
• Publication Number:
  US 20050245907A1
• Time in Patent Office: Days
• US Class Current: 604/891.100
• CPC Class Codes: A61M 5/14216 Reciprocating piston type
• CPC Class Codes: A61M 5/14276 specially adapted for implantation
• CPC Class Codes: F04B 17/042 the solenoid motor being separated from the fluid flow
• CPC Class Codes: F04B 53/1032 Spring-actuated disc valves F04B53/1022, F04B53/103 take precedence

Abstract

A drive mechanism for delivery of infusion medium has a coil and an armature moveable toward a forward position, in response to the electromagnetic field produced by activation of the coil. A piston is moveable axially within a piston channel to a forward position, in response to movement of the armature to its forward position. The armature and piston are moved toward a retracted position, when the coil is not energized. In the retracted position of the piston, a piston chamber is formed between the piston and a valve member and is filled with infusion medium. As the piston is moved to its forward position, the piston chamber volume is reduced and pressure within the piston chamber increases to a point where the pressure moves the valve member into an open position through an outlet.

Claims

1-49. -49. (canceled)

50. A drive mechanism for delivery of infusion medium comprising:

an inlet for receiving infusion medium;

an outlet for discharging infusion medium;

a piston channel through which infusion medium is communicated between the inlet and the outlet;

a piston located within the piston channel and defining a clearance between the piston and the piston channel in fluid flow communication with the inlet for receiving infusion medium from the inlet, the piston being moveable axially within the piston channel between an retracted position and a forward position, the piston defining a piston chamber at one end of the piston when the piston is in the retracted position, the piston chamber being in fluid flow communication with the clearance between the piston and piston channel for receiving infusion medium, wherein the piston chamber volume reduces as the piston is moved from its retracted position toward its forward position, to drive infusion medium from the piston chamber toward the outlet;

an armature located on one side of the piston channel and moveable between an retracted position and a forward position; and

a coil located in a position relative to the armature to generate an electromagnetic field upon energization sufficient to cause the armature and piston to move from their retracted positions to their forward positions;

wherein the clearance between the piston and the piston channel is sufficient to convey infusion medium to fill the piston chamber between coil activations.

51. A drive mechanism as recited in claim 50, wherein the radial clearance between the piston and the piston channel is within the range of about 0.003 and 0.01 of the diameter of the piston.

52. A drive mechanism as recited in claim 50, further comprising means for urging the piston and armature to return the piston and armature to their retracted positions upon deactivation of the coil and wherein the clearance between the piston and the piston channel is sufficient to convey infusion medium to fill the piston chamber as the piston returns from the forward position to the retracted position.

53. A drive mechanism as recited in claim 52, wherein said urging means comprises a spring.

54. A drive mechanism as recited in claim 52, wherein said urging means comprises a magnet.

55. A drive mechanism as recited in claim 50, wherein the coil surrounds the piston channel and piston.

69. A drive mechanism as recited in claim 50, wherein the piston has a diameter D_P and the piston channel has a diameter D_C and wherein D_P/D_C is within the range of about 0.990 and 0.995.

70. A drive mechanism as recited in claim 50, wherein the piston and the piston channel define a radial gap therebetween having an average of about 250 micro-inches annularly around the piston.

71. A drive mechanism as recited in claim 50, wherein the piston and the piston channel define a radial spacing therebetween having a size selected to allow the volume of medium received in the piston chamber from the inlet to be about 1 to 4 times a volume of medium that backflows into the piston channel from the piston chamber.

56-68. -68. (canceled)

72. A method for delivery of infusion medium comprising:

providing a housing and cover structure having an inlet for receiving infusion medium, an outlet for discharging infusion medium and a piston channel through which infusion medium is communicated between the inlet and the outlet;

arranging a piston within the piston channel and defining a clearance between the piston and the piston channel in fluid flow communication with the inlet for receiving infusion medium from the inlet;

receiving infusion medium in a piston chamber through the clearance between the piston and piston channel, the piston chamber being at one end of the piston when the piston is in the retracted position;

energizing a coil located in a position relative to the armature to generate an electromagnetic field in the area of the piston upon energization of the coil;

moving the piston axially within the piston channel between an retracted position and a forward position in response to the generation of an electromagnetic field by energizing the coil, to reduce the piston chamber volume as the piston is moved toward its forward position, to drive infusion medium from the piston chamber toward the outlet;

wherein the clearance between the piston and the piston channel is sufficient to convey infusion medium to fill the piston chamber between coil activations.

73. A method as recited in claim 72, wherein arranging the piston comprises arranging the piston such that the radial clearance between the piston and the piston channel is within the range of about 0.003 and 0.01 of the diameter of the piston.

74. A method as recited in claim 72, further comprising urging the piston and armature to return the piston and armature to their retracted positions upon de-energization of the coil and wherein arranging the piston comprises arranging the piston such that the clearance between the piston and the piston channel is sufficient to convey infusion medium to fill the piston chamber as the piston returns from the forward position to the retracted position.

75. A method as recited in claim 74, wherein urging the piston comprises providing a spring for urging the piston toward the retracted position.

76. A method as recited in claim 74, wherein urging the piston comprises providing a magnet for urging the piston toward the retracted position.

77. A method as recited in claim 72, wherein energizing a coil comprises energizing a coil that is arranged to surround the piston channel and piston.

78. A method as recited in claim 72, wherein defining a clearance comprises providing a piston having a diameter D_P and the piston channel having a diameter D_C, wherein D_P/D_C is within the range of about 0.990 and 0.995.

79. A method as recited in claim 72, wherein defining a clearance comprises providing a radial gap between the piston or the piston channel having an average of about 250 micro-inches annularly around the piston.

80. A method as recited in claim 72, wherein defining a clearance comprises providing a radial gap between the piston or the piston channel having a size selected to allow the volume of medium received in the piston chamber from the inlet to be about 1 to 4 times a volume of medium that backflows into the piston channel from the piston chamber.